FIG. 1 shows a first example of an industrial control system CS including an industrial automation controller 100 and a distributed industrial automation input/output (I/O) system 10 operatively connected to the industrial controller. The I/O system 10 includes a network adapter module 12 providing a connection 14 to an industrial data network 16. The data network 16 may be any one of a number of industrial control or I/O networks including but not limited to ControlNet, DeviceNet, EtherNet/IP, RIO, ASi, PROFIBUS, PROHnet, Foundation Fieldbus or the like as are well known in the art of industrial automation data networks. The adapter module 12 communicates over the network 16 with the industrial controller 100 to receive output data from the industrial controller or to provide input data to the industrial controller 100 to be processed according to a control program executed by a PLC and/or other processor(s) of the industrial controller 100. The network 16 can be hard-wired or wireless.
With respect to the I/O system, itself, the adapter module 12 communicates with a backplane circuit B (often referred to simply as the “backplane”) to operably connect the industrial controller 100 to one or more I/O modules 20 that are operably connected to the backplane B. In the illustrated embodiment, a physical base or chassis 18 is provided to contain the adapter module 12 and to contain the I/O modules 20. At least the I/O modules 20, and optionally also the adapter module 12, are selectively insertable and removable to/from the chassis 18 to provide the modularity required for customization, module repair/replacement, expansion capability, and the like.
The I/O modules 20 connect via I/O field lines 24 (e.g., electrical cables, fiber optic cables, etc.) with a controlled device or process 26a,26b,26c,etc. (generally 26) which can be a machine, a sensor, or another device or process, or several or portions of same. As is understood in the art, the I/O modules 20 convert digital data received over the backplane B from the controller 100 and adapter module 12 into output signals (either digital or analog) in a form suitable for input to an industrial process 26. The I/O modules 20 typically also receive digital or analog signals from an industrial process 26 and convert same to digital data suitable for transmission on the backplane B to the adapter module 12 and, thereafter, to the controller 100 for processing.
FIG. 2 is similar to FIG. 1 but shows an alternative industrial automation control system CS′ in which the industrial controller 100 is also mechanically connected to the chassis 18 and directly operably connected to the backplane B for communication of data to and from the I/O modules 20, in which case the adapter module 12 is eliminated. In such case, the industrial controller 100 and the I/O modules 20 communicate with each other directly over the backplane circuit B.
In either the example of FIG. 1 or FIG. 2, modularity of the I/O modules 20 with respect to the chassis 18 and backplane B is provided through an electrical module connector 28 on each I/O module 20 which may be mated with any one of a number of corresponding electrical backplane connectors 30 extending from and operatively connected to the backplane B. The backplane connectors 30 are each associated with a respective physical and logical module mounting location or “slot,” and the chassis 18 provides mechanical features (not shown) associated with each slot for mechanically releasably securing each I/O module 20 to the chassis 18 in its operative position.
Furthermore, for both of the above-described systems CS,CS′ of FIGS. 1 and 2, each I/O module 20, itself, includes multiple I/O communications channels 22a,22b,22c,etc. (generally 22), such that each I/O module 20 can be operably connected to communicate with a corresponding multiple number of field devices or processes 26. One deficiency of known systems is that the I/O channels 22 of each module 20 are manufactured with a select type (analog or digital, input or output) that cannot be altered after the module 20 is manufactured and that cannot be customized for a particular user's requirements. This limitation often requires that an end-user purchase more modules 20 than desired in order to have the required types of I/O channels for a particular application, even though certain I/O channels (of the type not needed for that particular application) are not being used. Another drawback associated with known systems is that a failure of one of the I/O channels 22a,22b,22c in a particular I/O module 20 requires that the entire I/O module 20 be removed and replaced, even though only one of the channels 22 of the module has failed. This is highly undesirable because replacement of an I/O module 20 for failure of a single channel 22 of the module creates a significant expense for replacement of the complete I/O module. Also, every device or process 26 connected to not only the faulty I/O channel 22 but also the properly functioning I/O channels 22 of the module 20 must be stopped and disconnected from the I/O module 20 until a replacement module 20 is installed, which typically also requires associated devices and processes 26 being controlled to be stopped until the I/O module 20 with the defective I/O channel 22 is replaced.